Project Summary/Abstract China's national HIV epidemic is evolving rapidly and is now driven by heterosexual transmission. Because an estimated 30-40% of people living with HIV (PLHIV) may not be aware of their infection, China faces a ?needle in the haystack? challenge to reach more undiagnosed PLHIV, particularly heterosexual PLHIV. One commonly used strategy for identifying undiagnosed PLHIV is partner notification. Currently, the Chinese national HIV policy for partner notification adopts a passive referral approach, wherein newly diagnosed HIV-positive patients suggest testing to their partners. However, several provinces have implemented provider-assisted referral, a more proactive and resource-intensive approach. Evaluating and rethinking approaches for HIV screening and partner notification is especially needed to reach undiagnosed women living with HIV, most of whom are unaware that they are at risk for HIV infection. This F31 project addresses critical research gaps. First, a secondary analysis of national routine HIV care data will be conducted to examine individual- and provincial-level factors related to partner notification and partner testing uptake. Two-level hierarchical generalized linear models will be constructed to identify bivariate and multivariable associations between partner notification service type and partner testing uptake. The hypothesis is that after controlling for other variables, participants who received provider-assisted partner notification services had a higher likelihood of partner testing uptake compared to participants who experienced the passive referral approach. Next, to explore women's experiences with HIV testing, partner notification, and diagnosis, a cross-sectional mixed methods study will be conducted. Surveys and interviews will be used to investigate how HIV-positive women were initially brought into HIV care and to identify variations in HIV risk. Given the need for improved HIV testing strategies in China, this study is an important endeavor to critically assess the current approaches for partner notification and HIV testing, especially for women. The findings from this project will characterize the ongoing real-world implementation and effectiveness of partner notification and HIV testing programs and suggest potential areas for improvement or additional intervention. This F31 award will prepare the applicant to pursue future work in implementation science research on the evaluation, adaptation, and scale up of partner notification and HIV testing services. After the completion of this two-year research and training fellowship, the applicant will have an advanced skillset in scientific communication, biostatistical methods, implementation science, and mixed methods research. A multidisciplinary mentoring team will prepare the applicant for research independence in a career as an HIV epidemiologist, implementation scientist, and academic mentor.